EndFatigue

One of a large family of carotenoids (found in carrots), beta carotene is the main one added to supplements. In proper dosing it can be helpful, and higher doses (to a point) are associated with increased longetivity.¹

Because beta carotene is part of a larger "family," however, taking very high doses of only one type can actually suppress the others and become problematic. For example, taking 25,000 units a day was associated with an increased risk of lung cancer. So more is not always better!

References

¹Ray AL, Semba RD, et al, "Low Serum Selenium and Total Carotenoids Predict Mortality among Older Women Living in the Community: The Women’s Health and Aging Studies," J Nutr, 2006; 136(1): 172-6